Thank you, working fine after UpdateLayout ()

You are using VisualTreeHelper, but at this time the Grid does not exist in the VisualTree.
Call pane.UpdateLayout before pane.FindControlByName or call the FindControlByName later
Marin

That's about my poor English :)

This is exactly what I do but I don't load DataTemplate from resources, I just read them with XamlReader from xml file.

            switch (e.NewState)

            {

                case TileState.Normal:

                    pane.ContentTemplate = GetTileTemplate(TileState.Normal, null);

                    break;

                case TileState.Minimized:

                    pane.ContentTemplate = GetTileTemplate(TileState.Minimized, null);

                    break;

                case TileState.Maximized:

                    pane.ContentTemplate = GetTileTemplate(TileState.Maximized, (List<ZLink>)pane.Tag);

                    break;

                default:

                    break;

            }

This is how I search a grid within template:

Grid grid = pane.FindControlByName<Grid>("CardGrid");

and searching method:

public static T FindControlByName<T>(this FrameworkElement element, string name) where T: FrameworkElement

        {

            if (element == null) return null;

            if (element.Name == name && element.GetType() == typeof(T)) return (T)element;

            FrameworkElement foundElement = null;

            for (int i = 0; i < VisualTreeHelper.GetChildrenCount(element); i++)

            {

                FrameworkElement visual = VisualTreeHelper.GetChild(element, i) as FrameworkElement;

                foundElement = visual.FindControlByName<T>(name);

                if (foundElement != null)

                    break;

            }

            return (T)foundElement;

        } 

When I lookup this variable in TileState.Maximized case, it's always null. I tried to do that in MaximizedStateChanged handler but this is also always null

TilePane pane = (TilePane)e.Element; // and so on

Grid grid = pane.FindControlByName<Grid>("CardGrid");

I don't know if this matters, but  I have changed TilePane's style and I put content to ToggleButton.Content:

<ToggleButton x:Name="MaximizedStateToggleButton" VerticalAlignment="Stretch" IsChecked="false" HorizontalAlignment="Stretch" VerticalContentAlignment="Stretch" HorizontalContentAlignment="Stretch" Padding="0">

                                <ig:Commanding.Command>

                                    <igTileView:TilePaneCommandSource EventName="Click" Parameter="Toggle" CommandType="Maximize"/>

                                </ig:Commanding.Command>

                                <ToggleButton.Content>

                                        <ContentPresenter x:Name="contentContentPresenter" HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" Margin="{TemplateBinding Padding}" VerticalAlignment="{TemplateBinding VerticalContentAlignment}" Grid.Row="0" Content="{TemplateBinding Content}" ContentTemplate="{TemplateBinding ContentTemplate}" Grid.Column="0"/>

                                </ToggleButton.Content>

                            </ToggleButton>